This invention relates to a disk augmentation system and method for providing support for reducing load on one or more disks in a patient's spine.
Human spines are formed from vertebrae, which are separated and cushioned from each other by disks. The disks consist of a fibrous outer envelope containing a gel-like fluid. The disks are subject to large forces, which may vary from about 175 pounds when a person is at rest to as high as about 500 pounds during activity. For example, a person who lifts a 15-pound weight one foot in front of such person, using a bending movement, can generate nearly 500 pounds of force on his or her spine. Because of the high forces on them, spinal disks commonly rupture, particularly as they deteriorate with age.
Various attempts have been made to deal with the problem of a diseased intervertebral disk. One standard procedure is to remove the disk and fuse the vertebrae, which were formerly separated by the disk. A difficulty with this is that relative motion between the two vertebrae is no longer possible, causing both stiffness in the spine and difficulties in areas above or below the fused disk.
Other attempts to deal with the problem have involved removing the diseased disk and replacing it with a prosthetic artificial disk made of a resilient material or mechanical articulation. The goal of such predicate devices is to replace the diseased disk with an artificial device of similar biomechanical function. A major problem with this approach is that it requires an extensive and technically demanding surgical procedure. Such a procedure consists of surgical exposure through the abdomen of the patient, which risks injury to abdominal structures and usually requires the services of a multidisciplinary surgical team. Meticulous and complete removal of the native disk is required prior to placement of such a device—a time consuming and technically difficult procedure.
Still other attempts to deal with the problem have included devices which place springs, flexible rods, or bands around the rear portion of the spine in order to share the load placed upon disks and their associated joints. These devices have the advantage of being relatively straightforward to place surgically through a rearward approach; however, they do not replicate the ideal biomechanical properties of a true prosthetic disk system. Some examples of prior systems related to disk augmentation are illustrated in U.S. Pat. Nos. 4,309,777, 4,759,769, 5,258,031, 5,415,661, 5,645,599, 5,928,284, 6,146,421, 6,231,609, 6,293,949, 6,419,704, 6,440,169, 6,540,785, 6,595,993, 6,572,653, and 6,610,093.
There is, therefore, a need for a system and method for facilitating reducing load on one or more disks in the spinal column by providing a rearwardly-placed external disk retainer and support system and method. Such a system will replicate the biomechanical properties of an intervertebral prosthetic disk with the simplicity and safety of a rearward approach.